With the development trend of compactness of the liquid crystal display, it needs fewer and fewer light emitting diodes (LEDs).
Referring to FIG. 1, in the side-light type LED backlight module, the decrease of the LED causes the increase of the pitch P′ between the LEDs. After the light is emitted from the LED 11′ to the light guide plate 12′, the refraction effect occurs because the density of the light guide plates 12′ is different to and generally smaller than the density of air.
A portion of light emitted from the LED 11′ perpendicularly enters the light guide plate 12′, and the opening angle of the portion of the vertical incident light is θair=90°. After the portion of the light enters the light guide plate 12′, the opening angle changes to θLGP=arcsin(1/nLGP), apparently θLGP<90°.
For the light concentrating around the portion of the vertical incident light, when the light mixing distance d maintains unchanged, the smaller θLGP is, the more easily the portion of the light distributes intensively in a certain range of the light guide plate 12′. As a result, it leads to the hotspot phenomenon in the liquid crystal display.
Thus, how to solve the technical problem of the traditional technology that the vertical incident light of the light guide plate and the light concentrating around the vertical incident light enter the light guide plate and then distribute intensively in a certain range of the light guide plate and thereby leads to the hotspot phenomenon in the liquid crystal display is one of the research trends in the technology field of liquid crystal display.